Hello My ¹8 Month Old Daughter Has Just Had Her

Hello my ¹8 month old daughter has just had her bottom changed and I have notice time black specks in her stool it kind of looks like little bits of black glitter very tiny she had diarrhea last week ànd has been çhangiñgfrom bottle to bottle if she feels like formula or cows milk she loves to make life hard should I be worried about this